Liquid volume measuring apparatus

ABSTRACT

Apparatus for determining deviation of a volume of liquid from a predetermined volume comprises a main vessel (4) for receiving the liquid and a measuring vessel (5) from which the deviation is determined from the meniscus of the liquid in the measuring vessel (5). A communicating tube (49) extending from a neck (32) of the main vessel (4) communicates the main vessel (4) with the secondary vessel (5) through a ball valve (56). Liquid above a weir (55) in the neck (32) flows into the measuring vessel (5). The deviation of the liquid volume is read from a scale (26) adjacent the measuring vessel (5). A variable volume bladder (71) completely filled with liquid alcohol is mounted in the main vessel (4) for compensating for volume changes in the main vessel (4) due to temperature variations.

The present invention relates to apparatus for determining volume of aliquid, and in particular though not limited to apparatus fordetermining the deviation of a volume of liquid from a predeterminedvolume. The invention also relates to a vessel, the volume of which issubstantially constant over a range of temperatures.

Apparatus for determining the deviation of a volume of liquid from apredetermined volume is typically used for checking the volumetricmeasuring accuracy of a dispensing and metering pump, such as, forexample, the metering pump of a petrol pump of the type used in theforecourt of a service station. Such apparatus, in general, comprisesone or more vessels of known volume. The quantity of liquid whosedeviation from a predetermined volume is to be determined is deliveredinto one of the vessels. A suitable scale is provided for enabling thedeviation in the volume of the liquid to be read. These known apparatussuffer from a number of disadvantages. In order to achieve therelatively high degree of accuracy required for determining thedeviation of volume, known apparatus tend to require a relatively highdegree of operator skill and have significant operational restrictions.

Furthermore, in general, such apparatus are calibrated at a predefinedtemperature, generally, 20° C. Where the apparatus is used at atemperature other than 20° C. during measuring of the volume of theliquid, the resultant volumes or deviations from a predetermined volumedetermined from the apparatus will be incorrect. In general, three mainfactors influence the temperature of the apparatus during measuring,firstly, the temperature of the ambient surrounds of the apparatus,secondly, and in many cases, more importantly, the temperature of theliquid being measured, and thirdly, the thermal response time of theapparatus. This thermal response time varies depending on the thermalconductivity of the material of the apparatus, in other words, the rateat which heat is transferred through the apparatus. For example, wherethe apparatus is to be used for determining the deviation of a volume ofpetrol from a predetermined volume, such apparatus, in general, arecalibrated at 20° C. It is quite common for the petrol to be at atemperature anywhere from 5° C., and even lower to 20° C. and evenhigher. Thus, even where an apparatus is stored at a temperature of 20°C., on coming into contact with the petrol, the temperature of theapparatus will be reduced or increased depending on the temperature ofthe petrol, and this will affect the volume of the apparatus, and inturn the accuracy of the apparatus.

Typical of such apparatus for measuring the deviation in volume of aliquid from a predetermined volume, known heretofore are disclosed inU.S. Pat. Nos. 1,377,577 and 4,928,514. In both cases, the apparatuscomprises a container which defines a relatively large hollow interiorregion for the liquid, and a neck extending upwardly from the containerwhich defines a throat to the hollow interior region of the container. Ascale which comprises plus and minus graduations, respectively, aboveand below a zero datum graduation is mounted in the neck, and enablesthe deviation of the volume of liquid from the predetermined volume tobe measured. The level of the meniscus of the liquid in the throat isread from the scale, and this gives the deviation above or below thepredetermined volume. Although, the transverse cross sectional area ofthe throat in both containers is somewhat less than the transverse crosssectional area of the hollow interior region of the container, it isstill relatively large. The accuracy of the results obtained from theseapparatus is relatively low. Firstly, because of the relatively largecross sectional area of the throat the vertical distance on the scalecorresponding to a unit deviation in volume is relatively small. Thus,without considerable operator skill, inaccuracies may occur when readingthe meniscus level from the scale. Secondly, because of the relativelylarge cross sectional area of the throat, an inaccurate reading ofdeviation will be obtained unless the container is level, in otherwords, unless the neck is extending in a vertical direction duringmeasuring.

European Patent Specification No. 0,472,353A discloses an alternativeconstruction of apparatus for determining the deviation of a volume ofliquid from a predetermined volume. The apparatus disclosed in thisEuropean specification requires two separate vessels namely, an outervessel into which the liquid is poured, and an inner vessel which isinserted into the outer vessel after the liquid has been poured into theouter vessel. An inlet to the inner vessel is provided at apredetermined height on the inner vessel, so that when the inner vesselis placed in the outer vessel, liquid flows into the inner vessel. Ascale is provided along the inner vessel which enables one, onwithdrawing the inner vessel, to read the deviation of the volume ofliquid from a predetermined volume. This apparatus, since it requirestwo completely separate vessels, is cumbersome to use, and requires asignificant level of operator skill. Furthermore, the apparatus is proneto considerable inaccuracy as a result of the fact that the accuracy ofmeasuring largely depends on the accuracy with which the inner vessel isinserted into and positioned in the outer vessel. An alternativeconstruction of this apparatus is also illustrated in the Europeanspecification. In the alternative construction, liquid is bled from theneck of a main vessel into a separate externally mounted graduatedbeaker from which the deviation is read. This apparatus suffers fromsubstantially similar disadvantages as the other apparatus disclosed inthis European specification. A further disadvantage of this alternativeconstruction of apparatus is that in certain cases it may provideinaccurate results. This is particularly so in cases where the volume ofliquid being measured is significantly less than the predeterminedvolume. In such cases the apparatus may indicate a deviation greaterthan the predetermined volume due to the fact that during delivery ofthe liquid into the apparatus some liquid may flow into the graduatedbeaker prior to the actual level of the liquid in the main vesselreaching a level in the neck at which flow should commence into thebeaker. In such cases, if the liquid level subsequently does not reachthe said level in the neck, the result will be inaccurate.

There is therefore a need for apparatus for determining the deviation ofa volume of liquid from a predetermined volume which overcomes Theproblems of the known apparatus just discussed, and other knownapparatus. There is also a need for apparatus for determining volume ofa liquid which overcomes the problems of known apparatus. There is alsoa need for a vessel, the volume of which is substantially constant overa range of temperatures. It is an object of the invention to provide anapparatus for determining deviation of a volume of liquid from apredetermined volume which overcomes some or all of the problems ofknown apparatus. In particular, it is an object of the invention toprovide apparatus for determining the deviation of a volume of liquidfrom a predetermined volume which is relatively accurate, relativelyeasy to use, and which requires the minimum of operator skills. It isalso an object of the invention to provide such an apparatus which islargely unaffected by change or variation in temperature of theapparatus and/or temperature differential between the apparatus and theliquid the deviation of which is being measured. It is further an objectof the invention to provide apparatus for determining the volume of aliquid which is relatively accurate, easy to use and may be used withminimum operator skills. It is also in object of the invention toprovide apparatus for determining volume of liquid which issubstantially unaffected by change or variation in temperature, and/ortemperature differential between the apparatus and the liquid the volumeof which is being determined. It is also an object of the invention toprovide a vessel, the volume of which is substantially constant over arange of temperatures.

According to the invention, there is provided apparatus for determiningvolume of a liquid, the apparatus comprising a container having a hollowinterior region for the liquid, and a scale means for determining thevolume of liquid in the container, characterized in that a temperaturecompensating means is provided for maintaining the volume of asubstantial portion of the hollow interior region of the containersubstantially constant over a range of temperatures, the temperaturecompensating means comprising a variable volume body member mounted inthe hollow interior region, the variable volume body member being of avolume, and being of a material, the volumetric temperature co-efficientof expansion of which is such that the change in volume of the variablevolume body member for each unit change in temperature is substantiallysimilar to the change in volume of the hollow interior region of thecontainer for each unit change in temperature.

The advantages of the invention are many. A particularly importantadvantage of the invention is that by virtue of the fact thattemperature compensating means is provided the volume of the hollowinterior region of the container remains substantially constant over arelatively large range of temperatures, and certainly over a range oftemperatures in the range of -5° C. to -35° C. Thus, the apparatus issuitable for accurately determining the volume of a liquid or foraccurately determining the volume of a deviation in the volume of aliquid from a predetermined volume irrespective of the temperature ofthe container and the temperature of the liquid. By virtue of the factthat the temperature compensating means comprises a variable volume bodymember, the volume and material of which, and the volumetric temperatureco-efficient of expansion of which is such that the change in volume ofthe variable volume body member for each unit change in temperature issubstantially similar to the change in volume of the hollow interiorregion of the container for each unit change in temperature, the volumeof the hollow interior region of the container is substantially constantat all temperatures of the container, and the liquid, the volume ofwhich or deviation in volume of which is being determined can beaccurately determined irrespective of the temperature differentialbetween the container and the liquid.

In another embodiment of the invention, the surface area of the variablevolume body member is such as to optimize the surface area of the bodymember exposed in the hollow interior region of the container.

The advantage of this feature of the invention is that it provides atemperature compensating means with a relatively rapid temperatureresponse time.

Preferably, the thermal response time of the variable volume body memberis relatively closely matched to the thermal response time of thecontainer which defines the hollow interior region.

The advantage of this feature of the invention is that there is littleneed to allow a settling time for the temperature of the liquid, thecontainer and the variable volume body member to equalize.

In another embodiment of the invention, the variable volume body memberdefines a hollow interior region for containing a heat expandable fluid,the outer volume of the variable volume body member being responsive tochange in volume of the heat expandable fluid.

The advantage of this feature of the invention is that it permits theuse of a variable volume body member of relatively small volume relativeto the volume of the hollow interior region of the container.

Preferably, the heat expandable fluid is a liquid. Advantageously, theheat expandable fluid is a liquid of relatively high volumetrictemperature co-efficient of expansion. Preferably, the heat expandablefluid is liquid alcohol.

The advantage of using liquid alcohol is that it has a relatively highvolumetric temperature co-efficient of expansion, and thus furthercontributes to allowing the volume of the variable volume body member tobe kept relatively small relative to the volume of the hollow interiorregion of the container.

In one embodiment of the invention, the variable volume body member isof sheet material and comprises at least one wall adapted to accommodatechange in the outer volume of the variable volume body member inresponse to change in volume of the heat expandable fluid so that thechange in the outer volume of the variable volume body membersubstantially corresponds to the free volumetric change in the volume ofthe heat expandable fluid contained therein in response to temperaturechange. The advantage of this feature of the invention is that theaffect of temperature change on the variable volume body member may besubstantially ignored.

In a further embodiment of the invention, the variable volume bodymember is of relatively thin wall construction. This further enables theeffect of temperature on the body member to be substantially ignored.

Preferably, the variable volume body member is an elongated memberextending between two ends.

The advantage of this feature of the invention is that it facilitatesheat transfer throughout the variable volume body member, thus improvingits temperature response time.

In another embodiment of the invention, the variable volume body memberis anchored at one end to a wall of the container defining the hollowinterior region. This is an advantageous construction of apparatus.

Preferably, the variable volume body member is anchored at both ends toa wall defining the hollow interior region of the container. Thisprovides an advantageous construction of apparatus.

In one embodiment of the invention, the variable volume body memberextends longitudinally between its ends and defines a substantiallystraight central axis. This feature of the invention provides arelatively convenient construction of apparatus.

In a further embodiment of the invention, the maximum transverse widthof the variable volume body member is relatively narrow relative to itslength.

The advantage of this feature of the invention is that it facilitatesheat transfer throughout the variable volume body member, thus improvingits temperature response time.

It is believed that it is preferable that the ratio of the maximumtransverse width of the variable volume body member to the length of thebody member should not exceed 50:1, and preferably, should not exceed20:1, and advantageously, should be approximately 13:1.

In one embodiment of the invention, the variable volume body member isof ovoid or circular transverse cross section. The advantage of thisfeature of the invention is that it further improves the temperatureresponse time of the variable volume body member.

Preferably, the variable volume body member is of hollow ovoid orcircular transverse cross section.

Alternatively, the transverse cross section of the variable volume bodymember may be substantially rectangular, and preferably, where the crosssection is rectangular, one dimension of the rectangular transversecross section may be considerably greater than the other dimensionperpendicular thereto. It is believed that an advantage of providing avariable volume body member of such a rectangular cross section would bethat better heat conduction into the heat expandable fluid would beachieved. This would thus improve the temperature response time of thevariable body member. This advantage would be achieved by virtue of thefact that a greater surface area per unit volume of the outer volume ofthe variable volume body member would be exposed in the main hollowinterior region. Heat exchange ribs may also be provided on the outersurface of the variable volume body member for improving heat conductioninto the body member, and in turn into the heat expandable fluid.

In one embodiment of the invention, the variable volume body member isof elastic material, and preferably, is of flexible, elastic material.Advantageously, the variable volume body member is of plastics material,preferably, a rubber or synthetic rubber material. The advantage ofproviding the variable volume body member of a flexible, and inparticular an elastic material, is that provided the modulus ofelasticity of the material is such the body member does not constrainthe free volumetric expansion of the heat expandable fluid. Thus, theheat expandable fluid can expand and contract as though it wereexpanding and contracting in free air.

In another embodiment of the invention, the variable volume body memberis of sheet metal material. The advantage of this feature of theinvention is that it provides a relatively robust variable volume bodymember, and where the metal material of the variable volume body memberis similar to the material of the container, the rate of heat transferto the container and the variable volume body member and the heatexpandable fluid contained therein is substantially similar, andaccordingly, the rate of change of volume of the variable volume bodymember and the container should be substantially similar. Additionally,where the metal has relatively high heat conductivity characteristics,the heat transfer to the heat expandable fluid is relatively rapid, andaccordingly, the temperature response time of the variable volume bodymember is short.

In one embodiment of the invention, the variable volume body membercomprises an elongated side wall extending between a pair of end walls,and advantageously, the side wall is of concertina type construction. Byproviding such a side wall, the body member has little affect on thefree expansion and contraction of the heat expandable fluid.

Preferably, a protective sleeve extends around and spaced apart from thevariable volume body member for protection thereof.

In another embodiment of the invention, the container comprises a mainvessel having a main hollow interior region for the liquid, and ameasuring vessel having a secondary hollow interior region of transversecross sectional area smaller than the maximum transverse cross sectionalarea of the main hollow interior region, the measuring vesselcommunicating with the main vessel through a communicating means forreceiving liquid from the main vessel, the communicating means defininga weir means over which liquid passes from the main hollow interiorregion to the secondary hollow interior region, the weir means beingpositioned to retain a known volume of liquid in the main hollowinterior region, the scale means being associated with the measuringvessel, and the temperature compensating means being provided in themain hollow interior region for maintaining the volume of the mainhollow interior region substantially constant over the range oftemperatures.

The advantage of having a main vessel and a measuring vessel is thatconsiderably improved accuracy in reading the volume or deviation involume from the apparatus is achieved. By virtue of the fact that thesecondary hollow interior region is of transverse cross sectional areasmaller than the maximum transverse cross sectional area of the mainhollow interior region, the difference in height of the meniscus of theliquid in the secondary hollow interior region for each unit change involume of liquid in the apparatus is considerably increased. Anadditional advantage of providing the apparatus with a main vessel and ameasuring vessel is that the two vessels may be of different material,for example the main vessel may be of a relatively strong, robustmaterial, for example, steel, stainless steel or the like, while themeasuring vessel may be of a transparent material, such as, for example,glass, plastics material or the like.

In one embodiment of the invention, the main vessel comprises a mainbulb defining a first hollow interior region and an elongated neckextending from the main bulb and defining an elongated throatcommunicating with the first hollow interior region, the first hollowinterior region and the throat forming the main hollow interior region,the communicating means communicating with the throat. This provides arelatively convenient construction of apparatus.

Preferably, the transverse cross sectional area of the throat adjacentthe communicating means is considerably smaller than the maximumtransverse cross sectional area of the first hollow interior region. Theadvantage of this feature of the invention is that it improves theaccuracy of the apparatus, and in particular, it improves the accuracyof use of the apparatus, in that it is not as critical that theapparatus should be level during use, in other words, it is not ascritical that the neck should extend vertically upwardly.

It is believed preferable that the ratio of the maximum transverse crosssectional area of the first hollow interior region to the transversecross sectional area of the throat adjacent the communicating means isat least 5:1, preferably, the ratio should be at least 10:1, andadvantageously, the ratio should be approximately 20:1.

In one embodiment of the invention, the measuring vessel comprises anelongated tubular member defining a longitudinally extending bore ofsubstantially constant transverse cross sectional area which forms thesecondary hollow interior region. The advantage of this feature of theinvention is that it provides a relatively accurate apparatus, andfurthermore, an apparatus that can readily easily be used with minimumoperator skills, and from which the volume or deviation in volume of theliquid can readily easily be read from the scale means.

It is believed preferable that the ratio of the maximum transverse crosssectional area of the first hollow interior region to the transversecross sectional area of the secondary hollow interior region is at least50:1, and preferably, should be at least 100:1, and advantageously,should be at least 200:1.

Advantageously, the tubular member of the measuring vessel is oftransparent material to facilitate viewing of the meniscus of the liquidin the measuring vessel.

In one embodiment of the invention, the scale means is provided adjacentthe tubular member of the measuring vessel. This facilitates ease ofreading of the level of the meniscus in the measuring vessel.

Advantageously, the scale means is adjustably mounted to facilitatecalibration of the apparatus.

In one embodiment of the invention, the communicating means comprises acommunicating tube extending between the measuring vessel and the neck.This provides a convenient and accurate construction of apparatus.Preferably, the communicating tube extends into the throat, andpreferably, the communicating tube terminates in a communicating openingin the throat.

The advantage of this feature of the invention is that it provides aparticularly accurate apparatus. This is particularly so where thetransverse cross sectional area of the throat is less than the maximumtransverse cross sectional area of the hollow interior region. In suchcases, since the liquid is being drawn from the main hollow interiorregion into the secondary hollow interior region through thecommunicating opening in the throat, it is not as critical that theapparatus be level during use, in other words, it is not as criticalthat the neck should extend vertically upwardly. Any minor deviationfrom level will not affect the result and reading obtained from theapparatus to any significant extent. Needless to say, the smaller thetransverse cross sectional area of the throat relative to the maximumtransverse cross sectional area of the main hollow interior region, theless critical it is that the apparatus be level during use.

In another embodiment of the invention, at least a portion of thecommunicating opening forms the weir means.

The advantage of this feature of the invention is that it provides aconvenient construction, as well as a robust construction of apparatus,and in certain cases facilitates calibration of the apparatus.

In another embodiment of the invention, the communicating opening liesin a substantially vertical plane. Alternatively, the communicatingopening lies in a substantially horizontal plane.

In one embodiment of the invention, the communicating opening liesadjacent the geometrical center of the throat. This provides aparticularly advantageous apparatus, in that the apparatus is relativelyaccurate, and is virtually unaffected by the positioning of theapparatus in use. In other words, whether the apparatus is level or notduring use has virtually no affect on the accuracy of the resultantreading obtained from the apparatus.

In another embodiment of the invention, inhibiting means is provided forselectively preventing passage of liquid into the secondary hollowinterior region of the measuring vessel. The advantage of providing theinhibiting means is that there is no danger of liquid inadvertentlysplashing into the measuring vessel during filling of the apparatus withthe liquid. It will be appreciated that should liquid splash into themeasuring vessel during filling, this could lead to an inaccurate resultin cases where the deviation in the volume of liquid below thepredetermined level was greater than the maximum negative deviation towhich the apparatus is provided to measure.

In one embodiment of the invention, the inhibiting means comprises avalve means, the valve means being operable between a closed positionisolating the secondary hollow interior region from the main hollowinterior region for inhibiting flow of liquid into the secondary hollowinterior region and an open position communicating the main andsecondary hollow interior regions. This provides a relatively convenientand robust construction of apparatus. Preferably, operating means isprovided for operating the inhibiting means. Advantageously, theoperating means is provided exteriorly of the apparatus. Preferably, theoperating means is manually operable.

In another embodiment of the invention, the inhibiting means is provideddownstream of the weir means, but adjacent thereto. In cases where theinhibiting means is provided downstream of the weir means, it isimportant that the inhibiting means should be located relatively closeto the weir means to avoid the danger of any excessive quantities ofliquid accumulating between the inhibiting means and the weir means as aresult of splashing during filling of the apparatus. Any suchaccumulation of liquid, as discussed above, could lead to an inaccurateresult being obtained in cases where the volume of liquid fell below thepredetermined volume to an extent greater than the maximum negativedeviation for which the apparatus is provided to determine. However, inmany cases, relatively minor accumulations of liquid between the weirmeans and the inhibiting means would not have a serious adverse effecton the results obtained from the apparatus, and in general, would nothave any effect on the results obtained from the apparatus where thevolume of the liquid being measured exceeded the volume of the mainhollow interior region up to the weir means.

Alternatively, the valve means is mounted in the communicating opening.The advantage of this feature of the invention is that there is littleor no danger of any liquid accumulating during filling which couldadversely affect the accuracy of the resultant reading obtained from theapparatus.

In one embodiment of the invention, main adjusting means is provided forvarying the volume of the main hollow interior region up to the level ofthe weir means for calibration of the apparatus. The advantage of thisfeature of the invention is that it provides for relatively easy andstraightforward calibration of the apparatus.

In one embodiment of the invention, the main adjusting means comprisesmeans for varying the height of the weir means in the throat. It is alsoenvisaged that a main adjusting means may be provided which wouldcomprise a piston or other member movable into and out of the mainhollow interior region for varying the volume of the main hollowinterior region during calibration.

In another embodiment of the invention, secondary adjusting means isprovided for varying the volume of the secondary hollow interior regionfor calibration of the apparatus. Preferably, the secondary adjustingmeans comprises a piston slidable in the measuring vessel for varyingthe volume of the secondary hollow interior region.

In one embodiment of the invention, the scale means comprises a scalefor determining the volume of liquid in the apparatus from the level ofthe meniscus of the liquid in the measuring vessel.

In another embodiment of the invention, the scale means comprises ascale for determining the deviation of the volume of liquid beingmeasured from a predetermined volume.

Additionally, the invention provides apparatus for determining volume ofa liquid, the apparatus comprising a main vessel having a main hollowinterior region for the liquid, a measuring vessel having a secondaryhollow interior region of transverse cross-sectional area smaller thanthe maximum transverse cross-sectional area of the main hollow interiorregion, the measuring vessel communicating with the main vessel througha communicating means for receiving liquid from the main vessel, thecommunicating means defining a weir means over which liquid passes fromthe main hollow interior region to the secondary hollow interior region,the weir means being positioned to retain a predetermined volume ofliquid in the main hollow interior region, and scale means beingprovided for determining the volume of liquid in the apparatus,characterized in that inhibiting means is provided for selectivelypreventing passage of liquid into the secondary hollow interior regionof the measuring vessel.

The advantage of this aspect of the invention is that it providesrelatively accurate apparatus which can be used by an operator withminimal operator skills, and which at the same time can producerelatively accurate results.

In one embodiment of the invention, the inhibiting means comprises avalve means, the valve means being operable between a closed positionisolating the secondary hollow interior region from the main hollowinterior region for preventing flow of liquid into the secondary hollowinterior region, and an open position communicating the main andsecondary hollow interior regions. Preferably, operating means isprovided for operating the valve means. Advantageously, the operatingmeans extends externally of the apparatus. Preferably, the operatingmeans is manually operable.

In one embodiment of the invention, the main vessel comprises a mainbulb defining a first hollow interior region and an elongated neckextending from the main bulb and defining an elongated throatcommunicating with the first hollow interior region, the first hollowinterior region and the throat forming the main hollow interior region,the communicating means communicating with the throat. Advantageously,the communicating means defines a communicating opening.

Preferably, the communicating opening defines the weir means.

In one embodiment of the invention, the communion-ting opening lies in asubstantially vertical plane. Preferably, the communicating opening liesin a substantiaily horizontal plane.

in another embodiment of the invention, the communicating opening is inthe throat Preferably the communication opening lies adjacent thegeometrical center of the throat. In another embodiment of theinvention, the communicating means comprises a communicating tubeextending between the measuring vessel and the neck. Preferably, thecommunicating tube extends into the throat.

In another embodiment of the invention, the weir means is provided inthe main vessel. Preferably, the weir means is provided in the throat.

In a further embodiment of the invention, the inhibiting means ismounted in the communicating opening. Preferably, the valve meanscomprises a valving member co-operable with the communicating openingfor closure thereof.

In one embodiment of the invention, the inhibiting means preventspassage of liquid into the secondary hollow interior region until theliquid level in the main hollow interior region at least reaches thelevel of the weir means.

The invention will be more clearly understood from the followingdescription of some preferred embodiments thereof, which are given byway of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of apparatus according to the invention fordetermining the deviation of a volume of liquid from a predeterminedvolume,

FIG. 2 is a side elevational view of the apparatus of FIG. 1,

FIG. 3 s a cross sectional side elevational view of the apparatus ofFIG. 1,

FIG. 4 s an underneath plan view of the apparatus of FIG. 1,

FIG. 5 is a cross sectional plan view of the apparatus of FIG. 1 on theline V--V of FIG. 3,

FIG. 6 is an elevational view of a detail of the apparatus of FIG. 1,not quite to scale,

FIG. 7 s a cross sectional view of another detail of the apparatus ofFIG. 1,

FIG. 8 is a cross sectional side elevational view of a further detail ofthe apparatus of FIG. 1,

FIG. 9 is a front elevational view of the detail of FIG. 8,

FIG. 10 is a perspective view of apparatus according to anotherembodiment of the invention for determining the deviation of a volume ofliquid from a predetermined volume,

FIG. 11 is a side elevational view of the apparatus of FIG. 10,

FIG. 12 is a front elevational view of the apparatus of FIG. 10,

FIG. 13 is a cross sectional side elevational view of the apparatus ofFIG. 10,

FIG. 14 is a cross sectional side elevational view of a detail of theapparatus of FIG. 10,

FIG. 15 is a cross sectional plan view of portion of the apparatus ofFIG. 10 on the line XV--XV of FIG. 13,

FIG. 16 is a cross sectional plan view of another portion of theapparatus of FIG. 10 on the line XVI--XVI of FIG. 13,

FIG. 17 is a front elevational view of a detail of the apparatus of FIG.10,

FIG. 18 is a cross sectional side elevational view of another detail ofthe apparatus of FIG. 10,

FIG. 19 is a plan view of the detail of FIG. 18 on the line IXX--IXX ofFIG. 18,

FIG. 20 is a cross sectional side view of a detail corresponding to thedetail of FIG. 18 for use in apparatus according to another embodimentof the invention,

FIG. 21 is a cross sectional plan view on the line XXI--XXI of FIG. 20,

FIG. 22 is a cross sectional side elevational view of a detail ofportion of an apparatus according to another embodiment of theinvention,

FIG. 23 is an end elevational view of the detail of FIG. 22,

FIG. 24 is a front elevational view of another detail for use inapparatus according to a still further embodiment of the invention,

FIG. 25 is a side elevational view of the detail of FIG. 24, and

FIG. 26 is a cross sectional view of the detail of FIG. 24 on the lineXXV--XXV of FIG. 23.

Referring to the drawings, and initially to FIGS. 1 to 9, there isillustrated apparatus according to the invention indicated generally bythe reference numeral 1 for determining volume of liquid. The apparatus1 in this embodiment of the invention is particularly suitable fordetermining the deviation of a volume of liquid from a predeterminedvolume, and is suitable for use in determining the volumetric meteringaccuracy of a metering pump, such as, for example, a petrol pump of thetype normally found in the forecourt of a service station. The apparatus1 comprises a support housing 2 for supporting a container 3 for theliquid. The container 3 comprises a main vessel 4 mounted substantiallywithin the support housing 2 and a measuring vessel 5 communicating withthe main vessel 4 and extending externally of the support housing 2 fromwhich the deviation in volume of the liquid being measured is determinedas will be described below.

The support housing 2 is formed in two parts, namely, a lower part 8 andan upper part 9 both of plastics material secured together by aplurality of rivets 10 along a seam 12 extending around the supporthousing 2. The support housing 2 is of substantially circular crosssection and tapers in a generally upwardly direction from the seam 12.Protrusions 14 formed in the lower portion 8 of the support housing 2extends sidewardly downwardly on opposite sides of the housing 2 andcarry respective feet 15 for supporting the apparatus 1. An elongatedhandle 18 of tubular stainless steel for carrying the apparatus 1extends substantially vertically and is secured by bracket members 20and 22 of stainless steel. The bracket member 20 extends from the lowerpart 8 of the support housing 2, and is secured thereto by a pair ofscrews 21, and is welded to the handle 18 at a lower end 19. The bracketmember 22 is described below. A third foot 23 extending downwardly fromthe handle 18 forms with the other two feet 15 a three point support forthe apparatus 1. A portion 25 extends outwardly of and substantiallyvertically along the support housing 2 for carrying a scale means,namely, an elongated scale member 26 adjacent the measuring vessel 5 fordetermining the deviation of the volume of liquid. The scale member 26is described in detail below.

The main vessel 4 is of stainless steel material of 0.9 mm wallthickness and comprises a main bulb 30 which defines a first hollowinterior region 31 of relatively large volume for accommodating most ofthe liquid. A neck 32 also of stainless steel and seam welded to themain bulb 30 at 29 extends upwardly from the main bulb 30 and defines athroat 33 of constant circular transverse cross section whichcommunicates with the first hollow interior region 31. The first hollowinterior region 31 and the throat 33 form a main hollow interior region34 of the main vessel 4.

The main bulb 30 is formed by a lower hemispherical portion 35 and anupper portion 36 of circular cross sectional area which tapers in agenerally upstream direction towards the neck 32. Flanges 37 and 38extending around the lower and upper portions 35 and 36, respectively,are secured together by a plurality of screws 39. The screws 39 alsoengage a flange 40 extending inwardly from the upper part 9 of thesupport housing 2 adjacent the seam 12 for securing the main vessel 4 inthe support housing 2. An annular seal 41 extending between the flanges37 and 38 seals the two portions 35 and 36 to provide a watertight firsthollow interior region 31. The transverse cross sectional area of thethroat 33 is considerably less than the maximum transverse crosssectional area of the first hollow interior region 31, namely, thetransverse cross sectional area extending in a plane through the flange37 of the lower hemispherical portion 35. This facilitates relativelyaccurate measuring of the deviation of the volume of liquid as will bedescribed below.

The measuring vessel 5 for measuring the deviation of the volume ofliquid in the apparatus i from the predetermined volume is formed by avertically extending elongated tubular member 43 of extruded transparentnylon material. A mounting bracket 42 locates and secures a lower end 46of the tubular member 43 to the bracket member 20. A longitudinallyextending bore 44 of constant circular cross section of the tubularmember 43 defines a secondary hollow interior region 45 for the liquid.The lower end 46 of the bore 44 is sealably closed by a secondaryadjusting means, namely, an adjusting piston 47 for enabling the volumeof the bore 44 to be varied, and in turn, the volume of the secondaryhollow interior region 45. The operation and construction of theadjusting piston 47 is described in more detail below.

A communicating means, namely, a communicating tube 49 of stainlesssteel communicates the secondary hollow interior region 45 with the mainhollow interior region 34. The communicating tube 49 extends from anupper end 50 of the measuring vessel 5 to the neck 32 of the main vessel4. The communicating tube 49 extends into the throat 33, and terminatesin a communicating opening 52 which lies in a substantially verticalplane in the throat 33 adjacent the neck 32. The communicating opening52 is defined by a rim 53, the lower portion of which forms a weir 55over which liquid passes from the main hollow interior region 34 intothe secondary hollow interior region 45. As will be described below, theweir 55 is located at a position in the throat 33 so that a known volumeof liquid, the volume of which is discussed below, is retained in themain hollow interior region 34 of the main vessel 4 by the weir 55.

Inhibiting means for selectively inhibiting the passage of liquid intothe secondary hollow interior region 45 during filling of liquid intothe apparatus 1, and until the level of liquid in the main hollowinterior region 34 at least reaches the weir 55, comprises a valvemeans, namely, a ball valve 56 of stainless steel which is located inthe communicating tube 49 relatively close to the communicating opening52. Operating means, namely, an operating handle 57 extends from theball valve 56 for manually operating the ball valve 56 between a closedposition with the secondary hollow interior region 45 isolated from themain hollow interior region 34 and an open position with the main andsecondary hollow interior regions 34 and 45, respectively,communicating.

The mounting bracket 22 is secured to an upper end 60 of the handle 18by a screw 62 and is welded to the communicating tube 49 by a nut 63.

The scale member 26 is secured by rivets 65 to the portion 25 of thesupport housing 2, and extends along and adjacent the measuring vessel 5for enabling the level of the meniscus of the liquid in the bore 44 tobe determined, for, in turn determining the deviation of volume of theliquid in the apparatus 1 from the determined volume. A plurality ofmain graduations 66a and 66b are provided on the scale member 26 atequi-spaced intervals and extend upwardly and downwardly, respectively,from a datum graduation 67. The datum graduation 67 corresponds to thelevel of the meniscus of the liquid in the measuring vessel 5 whichcorresponds to the position at which the meniscus of the liquid shouldsettle if the volume being measured is equal to the predeterminedvolume. The main graduations 66a above the datum graduation 67 indicatethe extent to which the volume of liquid in the apparatus 1 exceeds ordeviates above the predetermined volume, and the main graduations 66bbelow the datum graduations 67 indicate the extent to which the volumeof liquid falls or deviates below the predetermined volume. Intermediategraduations 68 are provided halfway between the main graduations 66a and66b.

Returning now to the measuring vessel 5, the adjusting piston 47 in thelower end 46 of the secondary hollow interior region 45 is of injectionmoulded plastics material. A pair of circumferentially extending grooves83 accommodate two O-ring seals 84 for sealably engaging the piston 47in the bore 44, see FIG. 7. A long shank screw 88 is engagable in athreaded bore 90 in the piston 47, and in a nut 91 secured to thebracket member 20, so that on rotation of the screw 88 in the nut 91,the position of the piston 47 in the bore 44 is varied. A lock nut 89 onthe screw 88 locks the screw 88 when the piston 47 is in the desiredlocation in the bore 44. The adjusting piston 47 is set in the bore 44during calibration of the apparatus 1 so that the portion of the bore 44between the lowest of the main graduations 66b, which in this caseindicates a deviation of -100 ml from the predetermined volume and thetop surface 94 of the piston 47 holds exactly 25 ml.

In this embodiment of the invention, the apparatus is sized to determinethe deviation of a volume of liquid from a predetermined volume, whichin this case is twenty liters. The main graduations 66a and 66b and theintermediate graduations 68 indicate the deviation in percentage amountsand in volume amounts from the predetermined volume. The maingraduations 66a and 66b indicate a range of deviations from +1% to -0.5%from the predetermined volume, and in volume terms from +200 ml to -100ml from the predetermined volume. Each main graduation 66a and 66b isarranged to indicate a 0.05% and a 10 ml deviation. Each intermediategraduation 68 measures 0.0254 deviation and 5 ml deviation.

Temperature compensating means for maintaining the volume of the mainhollow interior region 34 of the main vessel 4 substantially constantover a range of temperatures comprises a variable volume body member 70mounted in the main vessel 4. The body member 70 comprises an elongatedbladder 71 of circular cross section formed by a thin cylindrical sidewall 73 of a flexible, elastic material, namely, a synthetic rubber soldunder the Trade Mark VITON of 0.5 mm thickness. Ends 74 and 75 of thebladder 71 are secured to the main vessel 4 by anchor hooks 76 ofstainless steel welded to and extending from the main vessel 4 into themain hollow interior region 34. The bladder 71 defines a hollow interiorregion 77 which is completely filled with a heat expandable fluid, whichin this embodiment of the invention is liquid alcohol. The ends 74 and75 of the bladder 71 are sealed by a pair of clamping plates 78 and 79secured by rivets 80. An eye opening 81 in each clamping plate 78engages the corresponding anchor hook 76. The thickness of the syntheticrubber material of the side wall 73 and its modulus of elasticity arechosen so that the bladder 71 does not act as a constraint to the freevolumetric expansion and contraction of the alcohol in response totemperature change. In other words, the alcohol in the bladder 71 isfree to expand and contract in response to temperature change as thoughthe alcohol were in free air. Additionally, the volumetric temperatureco-efficient of expansion of the synthetic rubber material of thebladder 71 is significantly smaller than the volumetric temperatureco-efficient of expansion of the alcohol, and since the side wall 73 ofthe bladder 71 is relatively thin, the expansion and contraction of thebladder 71 itself due to temperature change may be ignored. The shape ofthe body member 70 is chosen to optimize the transfer of heat to andfrom the liquid alcohol to optimize the temperature response time of thebody member 70. The size, shape and outer volume of the bladder 71 ischosen taking account of the volumetric temperature co-efficient ofexpansion of the alcohol, so that the change in volume of the bladder 71resulting from the change in volume of the liquid alcohol for each unittemperature change is substantially similar to the change in volume foreach unit temperature change of the volume of the main hollow interiorregion 34 up to the level of the weir 55.

As discussed above, the apparatus 1 is for determining the deviation ofa volume of liquid from a predetermined volume of twenty liters. Thevolume of the main hollow interior region 34 of the main vessel 4 up tothe level of the weir 55 is chosen to accommodate the volume of thevariable volume body member 70 and the fact that the measuring vessel 5accommodates 125 ml of liquid up to the datum or zero graduation 67 onthe scale member 26. Therefore, the formula for deriving the outervolume v of the bladder 71 is as follows:

    (20,000-125+v)×0.48×10.sup.-4 =v ×11.8×10.sup.-4 v=843 ml

The volumetric expansion of stainless steel (material of the main vessel4) =0.48×10⁻⁴ per degree C.

Volumetric expansion of liquid alcohol =11.8×10⁻⁴ per degree C.

Accordingly, to accommodate the bladder 71, the volume of the mainhollow interior region 34 of the main vessel 4 up to the level of theweir 55 is approximately 20,843 ml. A small additional allowance involume to the main hollow interior region 34 is required to accommodatethe anchor hooks 76 and clamping plates 78 and 79. For each 1° C.temperature change, the volume of the main hollow interior region 34 upto the level of the weir 55 changes by 1 ml, which is identical to thechange of the outer volume of the bladder 71 for each 1° C. temperaturechange. Accordingly, the variable volume body member 70 compensatesfully for the change in volume of the main hollow interior region 34 upto the level of the weir 55 caused by each unit change in temperature.

In this embodiment of the invention, the maximum transverse crosssectional area of the main vessel 4 in the plane containing the flange37 is 38,000 mm². The transverse cross sectional area of the throat 33is 1,800 mm². The transverse cross sectional area of the bore 44 of themeasuring vessel 5 is 500 mm². Accordingly, the transverse crosssectional area of the throat 33 is considerably less than the maximumtransverse cross sectional area of the main hollow interior region 34 ofthe main vessel 4, and accordingly, since the main vessel 4 andmeasuring vessel 5 communicate in the throat 33, the accuracy of theapparatus 1 is relatively high. Since the transverse cross sectionalarea of the bore 44 of the measuring vessel 5 is relatively small, andconsiderably smaller than that of the throat 33 and, in particular, isvery considerably smaller than the maximum transverse cross sectionalarea of the main hollow interior region 34, a relatively accuratereading of deviation can be obtained. This is because a relatively smalldeviation from the predetermined volume results in a relatively largechange in the height of the meniscus of the liquid in the bore 44. Inthis particular embodiment of the invention, since the cross sectionalarea of the bore 44 is 500 mm², each 1 ml of deviation in volumecorresponds to a length of 2 mm on the scale member 26.

A closure cap 95 is provided for closing the neck 32 when the apparatus1 is not in use to avoid any danger of foreign bodies falling into themain vessel 4 or the escape of vapor therefrom.

In use, the apparatus 1 is initially calibrated. Once calibrated, nofurther calibration should be required unless the apparatus 1 isdamaged. The apparatus is calibrated as follows. The ball valve 56 isclosed. The apparatus 1 is placed in a controlled environment, thetemperature of which is 20° C., and levelled. In other words, theapparatus is arranged with the measuring vessel 5 and the neck 32extending vertically. A calibration volume of liquid, in this case,water or odorless kerosene is poured into the main vessel 4. The volumeof the calibration volume of liquid is exactly 20 liters. The ball valve56 is opened and the calibration liquid above the weir 55 flows over theweir 55 into the measuring vessel 4. At this stage, there should beprecisely 125 ml of calibration liquid in the bore 44. The position ofthe adjusting pistons 47 is adjusted upwardly or downwardly as the casemay require in the bore 44 until the meniscus of the liquid in the bore44 corresponds with the datum graduation 67. In this position, thereshould be 25 ml of calibration liquid between the top surface 94 of thepiston 47 and the lowest main graduation 66b, namely, the -100 mldeviation graduation. The adjusting piston 47 is secured in position inthe measuring vessel 5 by tightening the lock nut 89 against the nut 91.The calibration of the apparatus 1 is thus completed, and with the valve56 open the calibration liquid is emptied from the main vessel 4 and themeasuring vessel 5.

The apparatus is now ready for use.

Where it is desired to determine the deviation in volume of a volume ofliquid from a predetermined volume, the ball valve 56 is first closed.The volume of liquid is delivered into the main vessel 3, through thethroat 33. By virtue of the fact that the ball valve 56 is closed, thereis no danger of liquid splashing into the measuring vessel 5 while theliquid is being poured through the throat 33. It will be appreciatedthat liquid splash into the measuring vessel 5 during pouring couldresult in an inaccurate measurement should the deviation in volume ofthe liquid being measured be greater than 125 ml below the predeterminedvolume. On all the liquid having been poured into the main vessel 4, theball valve 56 is opened, and liquid above the weir 55 flows over theweir 55 in the measuring vessel 5. The level of the meniscus of theliquid in the bore 44 of the measuring vessel 5 is read against thescale member 26 to determine the deviation from the predeterminedvolume. A reading on the graduations 66a indicates the percentage amountand the volume amount by which the volume exceeds the predeterminedvolume, while a reading on the graduations 66b indicates the percentageamount and the volume amount by which the volume of liquid falls shortof the predetermined volume.

After the reading has been taken, the liquid in the apparatus 1 isdischarged by upending the apparatus 1. It is important that while theapparatus 1 is upended, the ball valve 56 should be in the open positionfor draining both the main vessel 4 and the measuring vessel 5. Once theapparatus 1 has been completely emptied of liquid, the apparatus 1 isthen ready for use again.

The advantages of the apparatus i according to this embodiment of theinvention are many. Firstly, the apparatus is of a relatively simpleconstruction, which necessitates minimal operator skills for use, whileat the same time producing relatively accurate results. Further, byvirtue of the simple construction of the apparatus 1, the apparatus isrelatively robust and virtually maintenance free and also simple to use.By virtue of the fact that the transverse cross sectional area of thebore 44 of the measuring vessel 5 is relatively small, and considerablysmaller than the maximum transverse cross sectional area of the mainhollow interior region 34 of the main vessel 4, a particularly accuratemeasurement of deviation of the volume of liquid from the predeterminedvolume is obtained. Furthermore, by virtue of the fact that the weir 55over which the main vessel 4 and the measuring vessel 5 communicate islocated in the throat 33 which is of cross sectional area substantiallyless than the maximum transverse cross sectional area of the main hollowinterior region 34, accuracy in the results is further improved.Additionally, any discrepancies in the level of the apparatus duringmeasuring, have a minimal affect on the resultant deviation measured.

A particularly important advantage of the invention is achieved byvirtue of the provision of the temperature compensating means in themain vessel. By virtue of the fact that the change in volume of thevariable volume body member 70 is substantially similar to the change involume of the main hollow interior region 34 of the main vessel 4 foreach unit change in temperature, the apparatus is accurate over a widerange of temperatures, and accordingly, the deviation of a volume ofliquid from a predetermined volume may be determined over a wide rangeof temperatures without the need for making compensations for thetemperature of the vessel and the temperature of the liquid beingmeasured.

Referring now to FIGS. 10 to 19, there is illustrated apparatusaccording to another embodiment of the invention indicated generally bythe reference numeral 101 also for determining the deviation of a volumeof liquid from a predetermined volume. The apparatus 101 is alsosuitable for determining the volumetric metering accuracy of a meteringpump, such as, for example, a petrol pump. The apparatus 101 comprises amain vessel 103 of stainless steel of 0.9 mm wall thickness forreceiving the liquid. The main vessel 103 is formed by a lower main bulb105 formed by a substantially spherical shell 106 which defines a firsthollow interior region 107 of relatively large volume for accommodatingmost of the liquid. Portion 109 of the shell 106 forms a ground engagingbase 110 for supporting the apparatus 101 in a substantially uprightposition as illustrated in FIGS. 11 to 13. Three ground engaging feet111 extend downwardly from the base 110 for engaging the ground. A neck112 extends upwardly from the spherical shell 106 and defines a throat114 which communicates with the first hollow interior region 107 fordelivering liquid into the first hollow interior region 107 and foremptying the liquid from the first hollow interior region 107. The firsthollow interior region 107 and the throat 114 form a main hollowinterior region 113 of the main vessel 103. The neck 112 defines threeregions, namely, a lower region 115 extending upwardly from the shell106, an intermediate region 116 extending upwardly from the lower region115 and slightly offset therefrom, and an upper region 117 whichterminates in an opening 119, and which is cranked to facilitate fillingand emptying of the main vessel 103. The throat 114 in all regions 115,116 and 117 is of circular transverse cross-section. As can be seen, thetransverse cross-sectional area of the throat 114 in the intermediateregion 116 is relatively small and considerably less than the maximumtransverse cross-sectional area of the first hollow interior region 107at 120.

A measuring vessel 122 for measuring the deviation of the volume ofliquid in the apparatus 101 from the predetermined volume is formed byan elongated tubular member 123 of transparent plastics material whichextends substantially vertically. A bore 124 of relatively small,constant, circular transverse cross-section extends longitudinally inthe tubular member 123 and forms a secondary hollow interior region 121.A lower end 125 of the bore 124 of the tubular member 123 is sealablyclosed by a plug 126. The upper end 127 of the tubular member 123extends into the throat 114 in the intermediate region 116 of the neck112 through an opening 108, and forms a communicating means, namely, acommunicating opening 128 for communicating the secondary hollowinterior region 121 of the measuring vessel 122 with the main hollowinterior region 113 of the main vessel 103. The upper end 127 of thetubular member 123 terminates in a rim 118 which defines thecommunicating opening 128. The rim 118 forms a weir means, namely, aweir 129 over which liquid passes from the main hollow interior region113 into the secondary hollow interior region 121. The communicatingopening 128 is located in the geometrical center of the transversecross-sectional area of the throat 114 adjacent the opening 128 tominimize the need for levelling of the apparatus during measuring aswill be described below.

Inhibiting means for selectively inhibiting the passage of liquid intothe secondary hollow interior region 121 of the measuring vessel 122until the volume of liquid to be measured has been completely deliveredinto the main hollow interior region 113 of the main vessel 103 isprovided by a valve means comprising a solid cylindrical valving member130. The valving member 130 terminates in a conical face 138 whichco-operates with the rim 118 for closing the communicating opening 128.A spindle 131 carrying the valving member 130 extends through an opening133 in the neck 112 and terminates in an operating means, namely, a knob132 to facilitate external manual operation of the valving member 130.The valving member 130 is movable from a closed position illustrated inFIG. 13 sealably engaging the rim 118 of the tubular member 123 forclosing the communicating opening 128, to an open position illustratedin FIG. 14 upwardly spaced apart from the rim 118 to permit flow ofliquid over the weir 129 from the main vessel 103 into the measuringvessel 122. A housing 134 mounted in the opening 133 in the neck 112slidably accommodates the spindle 131. A compression spring 135 ishoused in the housing 134 and acts between an end wall 150 of thehousing 134 and a flange 151 rigidly mounted on and extending around thespindle 131 for urging the valving member 130 into the closed position.

A sleeve 136 extending downwardly from the intermediate region 116 ofthe neck 112 around the opening sealably engages and slidablyaccommodates the tubular member 123 so that the tubular member 123 canbe moved in an upward and downward direction, namely, in the directionof the arrows A and B for calibration of the apparatus 101. By movingthe tubular member 123 in the direction of the arrows A and B, thevertical position of the weir 129 in the throat 114 is varied, and thus,the volume of the main hollow interior region 113 of the main vessel 103up to the level of the weir 129 is varied. A jubilee clip 137 around thesleeve 136 permits the tubular member 123 to be clamped in the sleeve136 with the weir 129 in the desired vertical position aftercalibration. A bracket 139 mounted on the shell 106 locates and securesthe end 125 of the tubular member 123.

Scale means comprising an elongated scale member 140 extendslongitudinally along both sides of the tubular member 123 for enablingthe level of the meniscus of the liquid in the measuring vessel 122 tobe determined for in turn, determining the deviation of the volume ofliquid in the apparatus 101 from the predetermined volume. The scalemember 140 is secured at its lower end to the bracket 139, and issecured at its upper end by a bracket 141 secured to the sleeve 136.Screws (not shown) adjustably secure the scale member 140 to thebrackets 139 and 141 to facilitate calibration of the apparatus as willbe described below. A plurality of main graduations 142a and 142b areprovided on both sides at equi-spaced intervals on the scale member 114and extend upwardly and downwardly from a datum graduation 143. Thedatum graduation 143 corresponds to the level of the meniscus of liquidin the measuring vessel 122 when the volume of the liquid is equal tothe predetermined volume. The main graduations 142a above the datumgraduation 143 indicate the extent to which the volume of liquid in theapparatus 101 exceeds or deviates above the predetermined volume, whilethe main graduations 142b below the datum graduation 143 indicate theextent to which the volume of liquid falls or deviates below thepredetermined volume. Intermediate graduations 144 are provided halfwaybetween the main graduations 142a and 142b.

In this embodiment of the invention, the apparatus is sized to determinethe deviation of a volume of liquid from a predetermined volume, thevolume of which is 10 liters. The main graduations 142a and 142b and theintermediate graduations 144 indicate the deviation in percentageamounts and in volume amounts from the predetermined volume. The maingraduations 142a and 142b indicate a range of deviations from +1% to-0.54 deviation from the predetermined volume, and in volume terms from+100 ml to -50 ml from the predetermined volume. Each main graduation142a and 142b is arranged to indicate a 0.05% and a 5 ml deviation. Themain graduation 142b corresponding to -0.54 and -50 ml deviationcoincides with a top surface 145 of the plug 126. Each intermediategraduation 144 measures 0.0254 deviation and 2.5 ml.

Temperature compensating means for maintaining the volume of the mainhollow interior region 113 of the main vessel 103 substantially constantover a range of temperatures comprises a variable volume body member 155formed by an elongated sealed hollow body member 156 filled with a heatexpandable fluid mounted in the first hollow interior region 107 of themain vessel 103. In this embodiment of the invention the heat expandablefluid is liquid alcohol. The body member 156 is of circular transversecross-section and is of sheet stainless steel of wall thickness 0.5 mm.The body member 156 comprises a pair of spaced apart end walls 157 and158 joined by a cylindrical side wall 159 which together with the endwalls 157 and 158 define a closed hollow interior region 160 which iscompletely filled with the liquid alcohol. A mounting member 162extending from the end wall 157 secures the body member 156 to the shell106 of the main vessel 103. The side wall 159 is of concertinaconstruction so that the body member 156 does not act as a constraint tothe free volumetric expansion and contraction of the alcohol in responseto temperature change. In other words, the alcohol is free to expand andcontract as though the alcohol were in free air. Additionally, thevolumetric temperature co-efficient of expansion of stainless steel issignificantly smaller than the volumetric temperature co-efficient ofexpansion of the alcohol, and since the body member 156 is of relativelythin wall stainless steel, the expansion and contraction of the bodymember itself due to temperature change may be ignored. The size, shapeand outer volume of the body member 156 is chosen taking account of thevolumetric temperature co-efficient of expansion of the alcohol so thatthe change in volume of the body member 156 resulting from the change involume of the liquid alcohol for each unit temperature change issubstantially similar to the change in volume for each unit temperaturechange of the volume of the main hollow interior region 113 up to thelevel of the weir 129. Additionally, the shape of the body member 156 ischosen so that the outer surface area of the body member 156 is such asto optimize heat transfer to and from the liquid alcohol to optimize thetemperature response time of the variable volume body member 155.

As discussed above, the apparatus 101 is for determining the deviationof a volume of liquid from a predetermined volume of ten liters. Thevolume of the main hollow interior region 113 of the main vessel 103 upto the level of the weir 129 is chosen to accommodate the volume of thevariable volume body member 155 and the fact that the measuring vessel122 accommodates 25 ml of liquid up to the datum or zero graduation 143on the scale member 140. Therefore, the formula for deriving the outervolume v of the variable volume body member 155 is as follows:

    (10,000-50+v)×0.48×10.sup.-4 =v×11.8×10.sup.-4 v =422 ml

The volumetric expansion of stainless steel (material of the main vessel103) =0.48×10⁻⁴ per degree C.

Volumetric expansion of liquid alcohol =11.8×10⁻⁴ per degree C.

Accordingly, to accommodate the variable volume body member 155, thevolume of the main hollow interior region 113 of the main vessel 103 upto the level of the weir 129 is approximately 10,422 ml. A smalladditional allowance in volume to the main hollow interior region 113 isrequired to accommodate the mounting member 162 of the variable volumebody member 155. For each 1° C. temperature change, the volumes of themain hollow interior region to the weir 129 and the body member 156 bothchange 0.5 ml. Therefore, the variable volume body member 155 fullycompensates for the change in volume of the main hollow interior region113 up to the level of the weir 129 caused by each unit change intemperature over a wide range of temperatures and certainly over a rangeof temperatures from -5° C. to +35° C. An advantage of providing thebody member 156 of a material similar to the material of the mainvessel, in this case, stainless steel is that the rate of heat transferfrom the petrol to the alcohol is substantially similar to the rate ofheat transfer from the petrol to the main vessel 103. Accordingly, therate of change of volume of the alcohol, and in turn the rate of changeof the volume of the body member 156 is substantially similar to therate of change of volume of the hollow interior region of the mainvessel 103. Thus, the change in volume of the main hollow interiorregion 113 of the main vessel 103 is relatively instantaneouslycompensated for by the change in volume of the variable volume bodymember 155.

In this embodiment of the invention, the maximum transverse crosssectional area of the main vessel 103 across the central plane of thespherical portion of the lower main bulb 105 is 42,000 mm². Thetransverse cross sectional area of the throat 114 in the neck region 116adjacent the weir 129 is 700 mm². The transverse cross sectional area ofthe bore 124 of the measuring vessel 122 is 100 mm². Accordingly, thetransverse cross sectional area of the throat 114 adjacent the weir 129is considerably less than the maximum transverse cross sectional area ofthe main hollow interior region 113 of the main vessel 103, andaccordingly, since the main vessel 103 and the measuring vessel 122communicate through the communicating opening 128 which defines the weir129, the accuracy of the apparatus 101 is relatively high. Since thetransverse cross sectional area of the bore 124 of the measuring vessel122 is relatively small, and considerably smaller than the throat 114adjacent the weir 129, and in particular, the main vessel 104, arelatively accurate reading of deviation can be obtained. This isbecause a relatively small deviation from the predetermined volumeresults in a relatively large change in the height of the meniscus ofthe liquid in the bore 124. In this particular embodiment of theinvention, since the cross sectional area of the bore 124 is 100 mm²,each 1 ml of deviation in volume corresponds to a length of 1 mm on thescale member 140. In other words, the intervals between adjacent maingraduations 142a and 142b is 1 mm. The distance between the intermediategraduations 144 and their adjacent main graduations 142a and 142b is 0.5mm.

A handle 146 of plastics material extends between the shell 106 and theupper region 117 of the neck 112 for carrying the apparatus 101.

In use, the apparatus 101 is initially calibrated. Once the apparatus101 has been calibrated, no further calibration should be requiredunless the apparatus 101 is damaged. The apparatus 101 is calibratedusing a two stage process as follows. The first stage of calibrationrequires accurate location of the position of the weir 129 in the throat114. The tubular member 123 with the plug 126 sealably secured thereinis inserted through the sleeve 136 into the throat 114 so that the weir129 is well above the position which would retain a first calibrationvolume of liquid, which in this case is 9,950 ml. The first calibrationvolume of liquid is delivered into the main vessel 103. With theapparatus level, the tubular member 123 is slowly moved downwardlythrough the sleeve 136 until the calibration liquid in the main vessel103 just commences to flow over the weir 129. The tubular member 123 isthen clamped in the sleeve 136 by tightening the jubilee clip 137, andthe calibration liquid is emptied from the apparatus 101. The housing134 with the spindle 131 carrying the valving member 130 and the knob132 mounted therein is inserted into and secured in the opening 133 ofthe neck 122. The second stage of the calibration process requiresdelivery of a second calibration volume of liquid into the main vessel103, the volume of which is exactly the predetermined volume, which inthis case is 10 liters. The second calibration volume is delivered intothe main vessel 103 with the valving member 130 closing thecommunicating opening 128. On the second calibration quantity of liquidbeing fully delivered into the main vessel 103, up to above the level ofthe weir 129, the valving member 130 is moved into the open position byraising the knob 132 upwardly of the neck 112. The valving member 130 isretained in the open position until the volume of the second calibrationliquid above the weir 129 has passed over the weir 129 into themeasuring vessel 122. The valving member 130 may then be closed byreleasing the knob 132. The apparatus should be level during thisoperation. The scale member 140 is longitudinally adjusted along thetubular member 123 until the datum graduation 143 co-incides with themeniscus of the liquid in the bore 124. The scale 140 is then secured inposition. The calibration liquid is discharged from the apparatus 101and the apparatus 101 is then ready for use.

The volume of liquid, the deviation of which from a predetermined volumeis to be determined is delivered into the main vessel 103. While theliquid is being delivered into the main vessel 103, the valving member130 under the action of the compression spring 135 remains in the closedposition, thus closing the communicating opening 128 to avoid splashingof liquid into the measuring vessel 122. It will be appreciated thatsplashing of liquid into the measuring vessel 122 during filling couldresult in an inaccurate measurement should the volume of liquid beingdelivered into the main vessel 103 fall below -0.54 of the predeterminedvolume. On the volume of liquid having been completely delivered intothe main vessel 103, and with the apparatus substantially level, thevalving member 130 is moved into the open position by raising the knob132 upwardly relative to the neck 112, thus allowing liquid above thelevel of the weir 129 to pass over the weir 129 into the measuringvessel 122. After all liquid above the weir 129 has passed into themeasuring vessel 122, the level of the meniscus in the measuring vessel122 is read against the scale 140 to determine the deviation from thepredetermined volume. A reading on the graduations 142a or theintermediate graduations 144 above the datum graduation 143 indicatesthe percentage amount and the volume amount by which the volume of theliquid exceeds or deviates above the predetermined volume. A reading onthe main graduations 142b or the intermediate graduations 144 below thedatum graduation 143 indicates the percentage amount and the volume bywhich the volume of the liquid falls or deviates below the predeterminedvolume.

After the reading has been taken, the liquid in the apparatus 101 isdischarged by upending the apparatus. It is important while theapparatus 101 is upended that the valving member 130 should be movedinto the open position for draining the measuring vessel 122. Theapparatus 101 is then ready for use again.

The advantages of the apparatus 101 according to this embodiment of theinvention are many, and are substantially similar to those achieved bythe apparatus 1. However, in this embodiment of the invention, anadditional advantage is achieved by virtue of the fact that the weir 129is located in the geometrical center of the throat 114 and the fact thatthe communicating opening 128 which forms the weir 129 is relativelysmall by comparison to the cross sectional area of the throat 114.Because of these two features, the need to have the apparatus 101completely level is avoided. In other words, it is not essential thatthe ground engaging base 110 of the main vessel 103 be supported on anabsolutely level surface. Even if the apparatus 101 is not level, inother words, if the portion 116 of the neck 112 is not extendingvertically upwardly, the fact that the communicating opening 128 is ofrelatively small cross sectional area, and in particular, is located inthe geometrical center of the throat 114 will not affect the accuracy ofthe deviation determined from the scale member 140 of the apparatus 101.By virtue of the fact that the position of the weir 129 formed by theend of the tubular member 123 is adjustable in the throat 114 of themain vessel 103, calibration of the apparatus 101 is relatively easilyachieved, and the tolerance to which the main vessel 103 should bemanufactured is not exceedingly critical. Furthermore, by virtue of thefact that the scale member is adjustable relative to the measuringvessel, calibration of the apparatus is further facilitated.

Referring now to FIGS. 20 and 21, there is illustrated a temperaturecompensating means for use in apparatus according to another embodimentof the invention. In this case the apparatus is identical to theapparatus 101, the only difference being in the temperature compensatingmeans. The temperature compensating means comprises a variable volumebody member 170 formed by an elongated bladder 171 which is mountedwithin the first hollow interior region 107 of the main vessel 103. Thebladder 171 is completely filled with a heat expandable fluid, namely,alcohol. The bladder 171 is of a flexible, elastic material namelysynthetic rubber similar to that of the bladder 71 of the apparatus 1and of wall thickness similar to that of the bladder 71. The bladder 171comprises a cylindrical wall 173 closed at one end 174. The other end175 is sealably secured to a circular disc 176 which in turn is mountedto the shell 106 of the main vessel 103 by a mounting member 178. Aprotective sleeve 180 or cage of circular cross-section extends aroundthe bladder 171 and is mounted to the shell 106 and extends downwardlyinto the first hollow interior region 107. A plurality of openings 181extend through the protective sleeve 180 for communicating the volume182 between the sleeve 180 and the bladder 171 with the first hollowinterior region 107. Slots 183 extending through the protective sleeve180 adjacent the shell 106 prevent collection of air adjacent the top ofthe sleeve 180. Otherwise, the construction and use of the apparatusaccording to this embodiment of the invention is identical to theapparatus 1 described with reference to FIGS. 10 to 19.

Referring now to FIGS. 22 and 23 there is illustrated portion of a neck32 of apparatus according to another embodiment of the invention whichis substantially similar to the apparatus 1 of FIGS. 1 to 9. The neck 32defines a throat 33 similar to the throat 33 of the apparatus 1. In thisembodiment of the invention, the communicating tube 249 forcommunicating the throat 33 with the hollow interior region 45 of themeasuring vessel 5 terminates in a flange 250 in the throat 33 which issecured to the neck 32. A bore 251 in the communicating tube 249terminates in a communicating opening 252 which communicates the mainhollow interior region of the main vessel with the measuring vessel.Weir means, in this embodiment of the invention provided by a weir 255,extends transversely across the opening 252, and liquid passing from themain hollow interior region 34 into the secondary hollow interior region45 passes over the weir 255. The weir 255 retains a known volume ofliquid in the main hollow interior region which as discussed above isless than the predetermined volume.

Referring now to FIGS. 24 to 26, there is illustrated a variable volumebody member 270 for use in apparatus according to a still furtherembodiment of the invention, which is substantially similar to theapparatus 1 of FIGS. 1 to 9. The variable volume body member 270 issubstantially similar to the variable volume body member 70 of theapparatus 1 of FIGS. I to 9, with the exception that the transversecross sectional area of the bladder 271 instead of being of circularcross section, is of substantially rectangular transverse cross section.As can be seen in FIG. 26, one of the transverse dimensions isconsiderably greater than the other perpendicular transverse dimension.In other words, the length 1 of the transverse cross section of thehollow interior region 177 is considerably greater than the breadth b.The height h of the hollow interior region 177 is considerably greaterthan both the length and the breadth, 1 and b, respectively. However, incertain cases, it is envisaged that the height h may not be all thatmuch greater than the length 1, and in certain cases, it is envisagedthat the height h and length 1 may be substantially equal. The materialof the bladder 271 is similar to that of the bladder 71, and the hollowinterior region 277 is completely filled with liquid alcohol. Theclamping plates 278 and 279 are identical to the clamping plates 78 and79 of the variable volume body member 70 of the apparatus 1.

While the transverse cross sectional area of the bore of the measuringvessel, namely, the bore of the secondary hollow interior region of theapparatus 1 of FIGS. 1 to 9 has been described as being 500 mm² incertain cases it is envisaged that the bore of the secondary hollowinterior region of the secondary measuring vessel 5 may be 200 mm² inwhich case the measuring vessel 5 would be capable of measuring adeviation from the predetermined volume in the range of -60 ml to +60ml, or a total deviation on either side of the datum of 120 ml, or anyother variation thereof.

It is envisaged that the main vessel 103 of the apparatus 101 may bemounted within a protective housing to avoid damage and the like to themain vessel 103. Such a protective housing may be of plastics or othersuitable material, and may, for example, be of injection moulded orrotationally moulded plastics material. In such cases, it is envisagedthat the main vessel 103 would be mounted within the protective housingso that the walls of the main vessel 103 would be spaced apart from thewalls of the protective housing. It is also envisaged that provisionwould be made in the protective housing to provide clear visual accessto the measuring vessel and the scale, and additionally, it is envisagedthat the knob 132 for operating the valving member 130 would extendthrough the protective housing. Indeed, one of the advantages ofenclosing the main vessel in a protective housing is that the wallsforming the main vessel may be of relatively thin gauge stainless steelmaterial.

It is envisaged that a spirit level may be provided on the apparatus 1and 101 to facilitate levelling of the apparatus, should this bedesired. A spirit level may be provided in any suitable location,however, a typical location would be adjacent the necks of therespective apparatus. It is also envisaged in certain cases that eitheror both apparatus may be mounted so as to be self-levelling, forexample, the main vessel may be gimbal mounted from a frameworkextending upwardly from a ground engaging base formed separately of themain vessel. Alternatively, the ground engaging base may be formedseparately of the main vessel, and the main vessel may be mounted in thebase member to be tiltable relative to the ground engaging base.

While the main vessels have been described as being of particular shapesand constructions, a main vessel of any other shape and construction maybe provided. Needless to say, a measuring vessel of any other shape andconstruction besides being formed by a tubular member may also beprovided. While it is preferable, it is not essential that the measuringvessel should be connected directly into the main vessel, the twovessels may be connected by any suitable connecting tube or othersuitable communicating means.

While the inhibiting means for preventing passage of liquid into themeasuring vessel has been described as being provided by a valve means,any other suitable inhibiting means may be provided. Indeed, in certaincases, it is envisaged that the inhibiting means may be provided by asplash cover or the like, which would prevent passage of liquid from themain vessel into the measuring vessel until the level of liquid in themain vessel reached the weir. This would avoid any danger of splashingof liquid into the measuring vessel during filling.

While the main vessel and measuring vessel have been described as beingof particular sizes, the vessels may be of any other suitable or desiredsizes and other relationships between the sizes of the two vessels maybe provided. While it is desirable that the communicating openingcommunicating the measuring vessel with the main vessel should be in athroat of relatively small cross-section, this is not essential.

While the weir means has been described as being formed by the end ofthe tubular member defining the communicating opening, the weir meansmay be formed by any other means. For example, in certain cases, it isenvisaged that the weir means may be formed by an opening through theside wall of the tubular member. Needless to say, other means of forminga weir means will be well known to those skilled in the art.

While the main vessel has been described as being of stainless steel,the main vessel may be of any other suitable material. Indeed, incertain cases, it is envisaged that the main vessel may be of a plasticsmaterial. However, where the main vessel is of a plastics material, itis preferable that the volumetric temperature co-efficient of expansionof the plastics material is relatively low, otherwise, the volume of thevariable volume body member of the temperature compensating means willbe relatively large. Additionally, it is envisaged that a disadvantageof providing the main vessel of a plastics material is the relativelylow thermal conductivity of the plastics material. This would tend toretard the rate of change of volume with respect to time for a unittemperature change to which the main vessel is subjected. Further, whilethe measuring vessel has been described as being of a plastics material,the measuring vessel may be of any other suitable material, and incertain cases, it is envisaged that the measuring vessel may be ofglass.

It is also envisaged in certain cases that it may not be necessary forthe measuring vessel to be of a transparent, or indeed, a translucentmaterial. For example, in certain cases, it is envisaged that scalemeans may be provided internally or externally of the measuring vesselfor enabling the level of the meniscus of the liquid in the measuringvessel to be determined. Such scale means may be a float means, whichwould float on the liquid in the measuring vessel, and which would carrya member which would extend externally of the measuring vessel and mayor may not carry a scale thereon. Alternatively, such scale means maycomprise electronic, optical, ultra-sonic or the like transducers fordetermining the level of the meniscus of the liquid in the measuringvessel, and a suitable visual display would be provided for displayingthe level of the meniscus of the liquid in the measuring vessel.

Needless to say, the transverse cross-sectional area of the throat, themeasuring vessel, the hollow interior region of the main vessel and anyother transverse cross-sectional areas may be of any other desired sizeand shape.

It will be appreciated that the main vessel and measuring vessels may beprovided of any desired volume which is suitable for accommodating thevolume of the predetermined volume from which deviation is to bemeasured.

The volume of the body member of the temperature compensating means willbe chosen to match the volume of the hollow interior region of the mainvessel from the formula

    (V+v-y)×a=v×b

where

V= volume of the main hollow interior region up to the level of the weirof the main vessel,

v= the outer volume of the body member of the temperature compensatingmeans,

y= the volume of the secondary hollow interior region up to the datum orzero graduation,

a= volumetric temperature co-efficient of expansion of the material ofthe main vessel

b= volumetric temperature co-efficient of expansion of the heatexpandable fluid in the body member of the temperature compensatingmeans.

The volume of the measuring vessel will also vary depending on theamount of deviation to be measured.

While the apparatus has been described for measuring the deviation of avolume of liquid from a predetermined volume, it will be readilyapparent to those skilled in the art that the apparatus may be used formeasuring the actual volume of a liquid. While the scale means has beenprovided to indicate the deviation in percentage terms and volume termsin ml, the scale may be provided to show the deviation in any othersystems of measurement. Needless to say, the scale may be adapted tosuit any range of deviations to be measured.

While a particular construction of temperature compensating means hasbeen described, any other suitable construction of temperaturecompensating means may be provided. It will of course be appreciatedthat other suitable heat expandable fluids may be used instead ofalcohol, and in certain cases, it is envisaged that the heat expandablefluid may be a gas instead of a liquid. Further, it will be appreciatedin certain cases that the variable volume body member may be provided bya solid block of heat expandable material.

While the apparatus has been described as comprising a main vessel and ameasuring vessel, in certain cases, the apparatus may be provided with asingle container, in which case, it is envisaged that scale means may beprovided in the neck of the container or in any other suitable locationin the container. In which case, the temperature compensating meanswould be provided in the interior region of the single container.

It is also envisaged that the invention may provide a single vessel thevolume of which is substantially constant over a range of temperatures.In such cases, the temperature compensating means would be provided inthe vessel, and generally, within a hollow interior region of thevessel.

We claim:
 1. Apparatus for determining volume of a liquid, the apparatus(1,101) comprising:a main vessel (4,103) having a main hollow interiorregion (34,113) for holding a predetermined volume of the liquid, ameasuring vessel (5,122) having a secondary hollow interior region(45,121) for receiving and measuring a volume of the liquid receivedfrom the main hollow interior region (34,113), the secondary hollowinterior region (45,121) being of transverse cross-sectional areasmaller than the maximum transverse cross-sectional area of the mainhollow interior region (34,113), a communicating means (49,123) forcommunicating the measuring vessel (5,122) with the main vessel (4,123),for accommodating the liquid from the main hollow interior region(34,113) to the secondary hollow interior region (45,121), a wear meansbeing formed by the communicating means (49,123) over which the liquidpasses from the main hollow interior region (34,113) to the secondaryhollow interior region (45,121), the weir means (55,129) beingpositioned for retaining the predetermined volume of liquid in the mainhollow interior region (34,113), and a scale means (26,140) cooperatingWith measuring vessel (5,122) for determining the volume of liquid inthe apparatus (1,101), wherein an inhibiting means (56,130) is providedand co-operates with the communicating means (49,123) for selectivelypreventing passage of liquid into the secondary hollow interior region(45,121) of the measuring vessel (5,122).
 2. Apparatus as claimed inclaim 1 characterized in that the inhibiting means (56,130) comprises avalve means (56,130), the valve means (56,130) being operable between aclosed position isolating the secondandary hollow interior region(45,121) from the main hollow interior region (34,113) for preventingflow of liquid into the secondary hollow interior region (45,121), andan open position communicating the main and secondary hollow interiorregions (34,45,113,121).
 3. Apparatus as claimed in claim 1characterised in that an operating means (57,132) is provided foroperating the inhibiting means (56,130) externally of the apparatus(1,101).
 4. Apparatus as claimed in claim 1 characterised in that themain vessel (4,103) comprises a main bulb (30,105) defining a firsthollow interior region (31,107) and an elongated nesk (32,112) extendingfrom the main bulb (30,105) and defining an elongated throat (33,114)communicating with the first hollow interior region (31,107), the firsthollow interior region (31,107) and the throat (33,114) forming the mainhollow interior region (34,113), the communicating means (49,123)communicating with the throat (33,114).
 5. Apparatus as claimed in anyof claims 1 characterised in that the communicating means (49,123)defines a communicating opening (52,128) located in the throat (33,114).6. Apparatus as claimed in claim 5 characterised in that thecommunicating opening (52,128) defines the weir means (55,129), and theinhibiting means (56, 130) co-operates with the communicating opening(49,123 123).
 7. Apparatus as claimed claims 1 characterised in that thetransverse cross sectional area of the throat (33,114) adjacent thecommunicating means (49,123) is considerably smaller than the maximumtransverse cross sectional area of the main hollow interior region(31,107).
 8. Apparatus as claimed in claims 1 characterised in that theratio of the maximum transverse cross sectional area of the main hollowinterior region (31,107) to the transverse cross sectional area of thethroat (33,114) adjacent the communicating means (49,123) is at least5:1.
 9. Apparatus as claimed in any of claim 1 characterised in that themeasuring vessel (5,122) comprises an elongated tubular member (43,123)defining a longitudinally extending bore (44,124) of substantiallyconstant transverse cross sectional area which forms the secondarybellow interior region (45,121).
 10. Apparatus as claimed in 1characterised in that the scale means (26,140) is provided adjacent themeasuring vessel (5,122) for determining the deviation of the volume ofliquid being measured from a predetermined volume by comparing the levelof the meniscus of the liquid in the measuring vessel (5,122) with thescale means (26,140).
 11. Apparatus as claimed claim 1 characterised inthat a secondary adjusting means (47) is provided for varying the volumeof the secondary hollow interior region (45) for calibration of theapparatus (1).